New component for keyboards and panels.

From where you are running LNC, PI or PC? . The same thing is happening to me, when I restarted, it again removed the permissions to write to input. Now I don't have PC in me apto. Or see him tomorrow I can see him and I'll explain better.

i use PC Linuxcnc2.8.4 Live cd
I wonder if the uinput module started working or not.

As far as I can tell you are running from a LIVE CD, so any changes are only effective while it is running.
I don't know if executing from a LIVE CD can modify permissions.

No, please type sudo chmod 0660 /dev/uinput, but don't reboot, because rebooting will remove permissions to write to the uinput file.
To verify that the permissions have changed, run the command ls -l /dev/uinput
If crw-rw---- 1 root root 10, 223 Aug 13 10:13 /dev/uinput appears, you already have permissions to write to the uiinput file.
Run LCN from the teminial:
linuxcnc /home/linuxcnc/linuxcnc/configs/xxx.ini
and this should appear
SET_EVBIT 34
SET_EVBIT 2
SET_EVBIT 3
SET_EVBIT 4
SET_EVBIT 50
SET_EVBIT 5
SET_EVBIT 6
SET_EVBIT 7
SET_EVBIT 31
SET_EVBIT 8
SET_EVBIT 9
SET_EVBIT 10
SET_EVBIT 20
SET_EVBIT 11
SET_EVBIT 52
SET_EVBIT 14

When using the 7i73 with MATRIX_KB with a 4x8 keypad I have solved the sendkeys.N.scan-event-MM issue, when I press any of the keys of that keypad it writes me the assigned character. Now what I don't quite understand is what is related to sendkeys.N.pin-event-MM. I have not been able to understand very well what is the use. I thought that its use was to create HAL pin and that they could be used as inputs to execute some action such as enable the machine etc. but when testing there is no answer. In the example of the SENDKEYS component, the only use is in:
setp sendkeys.0.pin-event-00 29 # Left Ctrl
setp sendkeys.0.pin-event-01 57 # Space
#Send Ctl + Space from one trigger
net clear-errors parport.0.pin.00.in sendkeys.0.trigger-00 sendkeys.0.trigger-01
Unfortunately, nowhere on the forum is there a use for the sendkeys.0.pin-event-MM parameter.

Sorry, I mean install from USB images. LinuxCNC 2.8.4 released

thank you for the advice I can now hit the response button.

but still like you said When turning off and on Access rights will not work.

Is there any way to call the 0660 permissions on startup?